Despite high compliance with screening programs there continues to be a high death rate from cancer. In the U.S., in 2010, there were an estimated 209,060 new cases of breast cancer diagnosed, with a mortality rate of about 20%. One problem with current screening programs is that existing methods detect cancer when it is too advanced to enable the use of optimal, less invasive treatment options. Early diagnosis of cancer is critical to reducing deaths resulting from the disease.
Existing methods for cancer detection vary depending on the organ affected. Current methods include biopsy, fecal occult blood testing, colonoscopy, computer-aided tomography, magnetic resonance imaging (“MRI”), x-ray mammography, and ultrasound. Current diagnostic technologies can only detect highly calcified tumors, can often be invasive, and are very expensive.
There are also methods known for detecting circulating tumor cells (“CTCs”). Due to the expression of specific mutations, CTCs allow the identification of the organ of origin and the stage of the disease. CTCs are an extremely rare occurrence of in human blood (1:109, or about 1 to about 2 CTCs in 1 mL of circulating blood). Detection of CTCs requires large sample volumes (about 7.5 mL), and current CTC-detection methods are slow, labor-intensive, and expensive.
Existing CTC detection methods generally involve BioMEMS technology (a subset of Micro Electro Mechanical System technology) and fall into one of three main categories: size-based, optically-based, and adhesion-based. Adhesion-based methods have high capture rates, however, flow rates must be reduced to provide sufficient time for the adhesion binding reaction to occur. Currently, adhesion based target cell capture devices use very low flow rates to increase capture rate, resulting in extended processing times.
Several studies have demonstrated CTC-capture using microfluidic devices to identify the presence of human breast cancer, and the CellSearch™ immunomagnetic system is approved by the Food and Drug Administration (FDA) for monitoring post-treatment therapy, but all of the systems reported have either a long diagnosis time or unacceptable capture rates.
Therefore, there is a long-standing but unmet need for methods and devices for detecting early-stage cancer, which can accurately, economically, and quickly detect the presence of cancer cells.